The separation of small, polar organic molecules such as acetic acid from aqueous mixtures can be quite complicated and expensive, especially for dilute aqueous mixtures. For example, to separate acetic acid from water by distillation requires that the lower boiling point water be distilled away before the acetic acid can be recovered.
In addition to acetic acid, other small carboxylic acids (e.g., C3-C6 carboxylic acids, including lactic acid, hydroxybutyric acid, and the like) and lower alcohols like ethanol, isobutanol, and other C3-C6 alcohols, and aromatic compounds such as hydroxymethyl furfural, and vanillin are also often obtained or produced in aqueous mixtures such as fermentation broths or by aqueous processing of plant materials. It is difficult and expensive to separate such organic molecules from their aqueous mixtures.
There thus remains a tremendous need for efficient methods for extracting small, polar organic molecules from aqueous mixtures. There is a particular need for methods that permit easy recovery of fermentation products from aqueous mixtures. The present invention addresses many of these issues.